<html>
<script>
var obj = { a: {a: "hello", b: 21} };

var initalObj = Object.assign({}, obj);

initalObj.a.a = "changed";

console.log(obj.a.a); // "changed"

function deepClone(initalObj, finalObj) {
    var obj = finalObj || {};
    for (var i in initalObj) {
        var prop = initalObj[i];

        // 避免相互引用对象导致死循环，如initalObj.a = initalObj的情况
        if(prop === obj) {
            continue;
        }

        if (typeof prop === 'object') {
            obj[i] = (prop.constructor === Array) ? [] : {};
            arguments.callee(prop, obj[i]);
        } else {
            obj[i] = prop;
        }
    }
    return obj;
}

var result = deepClone(initalObj);

result.a.a = "Jerry";
console.log(result);
console.log(initalObj);

function deepClone2(initalObj, finalObj) {
    var obj = finalObj || {};
    for (var i in initalObj) {
        var prop = initalObj[i];

        // 避免相互引用对象导致死循环，如initalObj.a = initalObj的情况
        if(prop === obj) {
            continue;
        }

        if (typeof prop === 'object') {
            obj[i] = (prop.constructor === Array) ? [] : Object.create(prop);
        } else {
            obj[i] = prop;
        }
    }
    return obj;
}

var class2type = {};
var hasOwn = Object.prototype.hasOwnProperty;

var jQuery = {
	isArray: Array.isArray || function( obj ) {
		return jQuery.type(obj) === "array";
	},
	isWindow: function( obj ) {
		return obj && typeof obj === "object" && "setInterval" in obj;
	},
	isPlainObject: function( obj ) {
		// Must be an Object.
		// Because of IE, we also have to check the presence of the constructor property.
		// Make sure that DOM nodes and window objects don't pass through, as well
		if ( !obj || jQuery.type(obj) !== "object" || obj.nodeType || jQuery.isWindow( obj ) ) {
			return false;
		}

		try {
			// Not own constructor property must be Object
			if ( obj.constructor &&
				!hasOwn.call(obj, "constructor") &&
				!hasOwn.call(obj.constructor.prototype, "isPrototypeOf") ) {
				return false;
			}
		} catch ( e ) {
			// IE8,9 Will throw exceptions on certain host objects #9897
			return false;
		}

		// Own properties are enumerated firstly, so to speed up,
		// if last one is own, then all properties are own.

		var key;
		for ( key in obj ) {}

		return key === undefined || hasOwn.call( obj, key );
	},
	type: function( obj ) {
		return obj == null ?
			String( obj ) :
			class2type[ toString.call(obj) ] || "object";
	}
};

var extend = function() {
    var options, name, src, copy, copyIsArray, clone,
        target = arguments[ 0 ] || {},
        i = 1,
        length = arguments.length,
        deep = false;

    // Handle a deep copy situation
    if ( typeof target === "boolean" ) {
        deep = target; // true

        // Skip the boolean and the target
        target = arguments[ i ] || {};
        i++;
    }

    // Handle case when target is a string or something (possible in deep copy)
    if ( typeof target !== "object" && !jQuery.isFunction( target ) ) {
        target = {};
    }

    // Extend jQuery itself if only one argument is passed
    if ( i === length ) {
        target = this;
        i--;
    }

    for ( ; i < length; i++ ) {

        // Only deal with non-null/undefined values
        if ( ( options = arguments[ i ] ) != null ) {

            // Extend the base object
            for ( name in options ) {
                src = target[ name ];
                copy = options[ name ];

                // Prevent never-ending loop
                if ( target === copy ) {
                    continue;
                }

                // Recurse if we're merging plain objects or arrays
                if ( deep && copy && ( jQuery.isPlainObject( copy ) ||
                    ( copyIsArray = jQuery.isArray( copy ) ) ) ) {

                    if ( copyIsArray ) {
                        copyIsArray = false;
                        clone = src && jQuery.isArray( src ) ? src : [];

                    } else {
                        clone = src && jQuery.isPlainObject( src ) ? src : {};
                    }

                    // Never move original objects, clone them
                    target[ name ] = extend( deep, clone, copy );

                // Don't bring in undefined values
                } else if ( copy !== undefined ) {
                    target[ name ] = copy;
                }
            }
        }
    }

    // Return the modified object
    return target;
};

var result2 = extend(true, {}, initalObj);
result2.a.a = "i042416";
console.log(initalObj);
console.log(result2);
</script>
</html>